Experimental investigations on partial discharge characteristics of water droplets on polymeric insulating surfaces at AC, DC and combined AC-DC voltages

Abstract

Water droplets on polymeric insulating surfaces provide an intensified E-field stress at the common interface between water droplet, insulating surface and surrounding air, which may lead to partial discharges, surface deterioration or even flashover. While intensive research has been performed for the AC case and also for the DC case, a new kind of stress may arise by the combination of both, which is present when a DC and an AC system are installed on the same tower. Water droplet deformations at AC, DC and combined AC-DC voltages as well as their PD characteristics are experimentally investigated and discussed in this contribution. The water droplet at AC voltage oscillates at different oscillation modes, while it elongates towards electrodes at DC voltage. The deformation under combined AC-DC voltage stress consists of an oscillation superimposed to an elongation towards the electrodes. The water droplet elongates towards the AC electrode when the polarity of DC source is negative, while it elongates towards the DC electrode in case of positive DC voltage. Oscillation modes of the water droplet at AC voltage have an influence on its PD inception E-field strength. Under DC stress the PD signals consist of two or more different PD levels which are due to the differently sharped edges of the deformed water droplet. Increasing the DC component at combined AC-DC voltage provides a lower PD inception E-field strength. Conductive water droplets have lower PD inception values in comparison with non-conductive ones under AC-DC stress.Index Terms -Water droplet, polymeric insulating surfaces, PD inception E-field strength and combined AC-DC voltage.

Breakdown Voltage and Its Influencing Factors of Thermally Aged Oil-Impregnated Paper at Pulsating DC Voltage

“…The valve-side windings in a converter transformer withstand the voltage of complex waveforms [5]. The turn-to-ground insulation of the valve-side wingdings withstands pulsating DC voltage [5,6], also known as combined AC-DC voltage or AC and DC combined voltages [7][8][9][10]. The breakdown characteristics of OIP at pulsating DC voltage show many differences compared with that at AC voltage [6].…”

Performance analysis of epoxy nanocomposites due to water droplet‐initiated discharges under AC and DC voltages and localisation of discharges

“…It is observed that CIV increases with an increase in supply voltage frequency. Nazemi et al [9] have clearly observed that there exist different modes of oscillation of water droplet sitting on the surface of the sample. Under AC stress, water droplet elongates at the edges, along with the axis of the electrodes which results in electric field intensification at the triple junction of the surface, water, and air.…”

“…The deposition of discrete water droplets due to the wetting mechanisms such as rain or condensation of fog etc. over the surface of polymeric insulators such as epoxy leads to the local electric field intensification at the triple junction existing between insulating surface, water droplet, and surrounding air, causing the corona discharge, surface deterioration, and eventually the failure of an insulator [9]. Thus it is essential to understand the voltage at which the water droplet (of different conductivities) initiates discharges, which is called as corona inception voltage (CIV), under AC, DC, and under high-AC voltages of different frequencies.…”

Evaluation of Flashover Voltage Levels of Contaminated Hydrophobic Polymer Insulators Using Regression Trees, Neural Networks, and Adaptive Neuro-Fuzzy

“…Many environmental factors such as conductivity (μS/cm) of water droplets, droplets number, water droplet volume (ml), and percentage ratio of silicone rubber contents to the composite polymer have a strong impact on determining the the flashover voltages values of polymer insulators [9][10]. Consequently, the authors of this work are motivated to consider and develop numerical evaluation or accurate modeling of flashover voltages levels plays a significant role in studying the dynamic behavior of polymeric materials.…”

“…The root mean square error (RMSE) and the relative error (RE) is calculated according to (9) and (10) respectively. The correlation coefficient (R) is calculated according to (11), in which the superscript e refers to the estimated or predicted values, and t refers to the tested data values.…”